US12572750B2ActiveUtilityA1

Large language model evaluation with enhanced interpretability by k-nearest neighbor search

49
Assignee: IBMPriority: Feb 27, 2023Filed: Feb 27, 2023Granted: Mar 10, 2026
Est. expiryFeb 27, 2043(~16.6 yrs left)· nominal 20-yr term from priority
G06F 40/30G06N 3/08G06N 20/00G06F 16/35G06F 16/3344G06N 3/09G06N 3/045G06F 40/284G06F 40/20G06F 40/40
49
PatentIndex Score
0
Cited by
47
References
24
Claims

Abstract

Techniques for fine-tuning free evaluation of large language models with enhanced interpretability using a debiased output probability distribution of a large language model and a probability distribution of a k-Nearest Neighbor search result are provided. In one aspect, a method for performing a downstream task with a language model includes: constructing a datastore by applying the language model to a training set; applying the language model to a prompt-applied sentence from a testing set to obtain a language model feature vector; performing a k-Nearest Neighbor search of the datastore using the language model feature vector as a query vector; and interpolating a probability distribution of results from the k-Nearest Neighbor search and an output probability distribution of the language model to obtain a prediction for the downstream task.

Claims

exact text as granted — not AI-modified
What is claimed is: 
     
         1 . A method for performing a downstream task with a language model, the method comprising:
 obtaining a dataset for the downstream task, the dataset comprising at least a training set and a testing set;   constructing a datastore by applying the language model to the training set, the datastore comprising a set of triplets with each triplet including an instance x train  from the training set, a label y′, and a feature vector h train , and wherein the feature vector h train  corresponds to a masked token in the sentence x train ;   applying the language model to a prompt-applied sentence prompt(x) from an instance x in the testing set to predict a label y and a large language model feature vector h LLM (prompt(x));   computing an output probability distribution P LM  of the language model;   debiasing the output probability distribution P LM  of the language model to obtain a debiased output probability distribution {circumflex over (p)} debiasedLM ;   performing a k-Nearest Neighbor search of the datastore using the feature vector h LLM  prompt(x)) as a query vector to find k-Nearest Neighbors N;   computing a probability distribution {circumflex over (p)} kNN  of results from the k-Nearest Neighbor search, wherein {circumflex over (p)} kNN  is computed as:   
       
         
           
             
               
                 
                   p 
                   ^ 
                 
                 kNN 
               
               = 
               
                 
                   1 
                   
                     
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                       "\[LeftBracketingBar]" 
                     
                     𝒩 
                     
                       ❘ 
                       "\[RightBracketingBar]" 
                     
                   
                 
                 ⁢ 
                 
                   
                     ∑ 
                       
                   
                   
                     
                       ( 
                       
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                         , 
                         
                           y 
                           ′ 
                         
                         , 
                         
                           h 
                           train 
                         
                       
                       ) 
                     
                     ∈ 
                     𝒩 
                   
                 
                 
                   
                     y 
                     = 
                     
                       y 
                       ′ 
                     
                   
                 
                 
                   exp 
                   ⁡ 
                   ( 
                   
                     
                       - 
                       
                          
                         
                           
                             h 
                             train 
                           
                           - 
                           
                             
                               h 
                               LM 
                             
                             ( 
                             
                               prompt 
                               ⁢ 
                                   
                               
                                 ( 
                                 x 
                                 ) 
                               
                             
                             ) 
                           
                         
                          
                       
                     
                     T 
                   
                   ) 
                 
                 ⁢ 
                     
                 using 
                 ⁢ 
                     
                 T 
               
             
           
         
       
       as a scaling hyperparameter;
 interpolating the debiased output probability distribution {circumflex over (p)} debiasedLM  and the probability distribution {circumflex over (p)} kNN  to obtain a final prediction {circumflex over (p)}(y|prompt(x)) for the downstream task; and 
 outputting the results from the k-Nearest Neighbor search to explain the final prediction of the language model. 
 
     
     
         2 . The method of  claim 1 , wherein parameters of the language model are frozen. 
     
     
         3 . The method of  claim 1 , further comprising:
 extracting an instance x from the testing set; and   applying a prompt to the instance x to obtain the prompt-applied sentence prompt(x).   
     
     
         4 . The method of  claim 1 , wherein the label y is predicted from a pre-defined label set Y. 
     
     
         5 . The method of  claim 4 , wherein the output probability distribution P LM  is computed over a vocabulary V as P LM (y∈V|prompt(x)). 
     
     
         6 . The method of  claim 1 , wherein {circumflex over (p)} debiasedLM =W debias P LM (y∈V|prompt(x)), wherein W debias =diag({circumflex over (p)} cf ) −1  in which diag(v) is a function that returns a diagonal matrix of v, and wherein {circumflex over (p)} cf  is computed from {circumflex over (p)} cf =1/C Σc=1   C P LM (y|prompt(context c )) by giving different input texts prompt(context c )) to the language model where context c  is context-free input. 
     
     
         7 . The method of  claim 1 , wherein k is a number of instances, and wherein k∈{0,1,4,8}. 
     
     
         8 . The method of  claim 1 , wherein {circumflex over (p)}(y|prompt(x))=λ*{circumflex over (p)} debiasedLM + (1−λ)*{circumflex over (p)} kNN , and wherein λ∈[0,1]. 
     
     
         9 . A computer program product for performing a downstream task with a language model, the computer program product comprising a computer readable storage medium having program instructions embodied therewith, the program instructions executable by a computer to cause the computer to perform:
 obtaining a dataset for the downstream task, the dataset comprising at least a training set and a testing set;   constructing a datastore by applying the language model to the training set, the datastore comprising a set of triplets with each triplet including an instance x train  from the training set, a label y′, and a feature vector h train , and wherein the feature vector h train  corresponds to a masked token in the sentence x train ;   applying the language model to a prompt-applied sentence prompt(x) from an instance x in the testing set to predict a label y and a large language model feature vector h LLM (prompt(x));   computing an output probability distribution P LM  of the language model;   debiasing the output probability distribution P LM  of the language model to obtain a debiased output probability distribution {circumflex over (p)} debiasedLM ;   performing a k-Nearest Neighbor search of the datastore using the feature vector h LLM (prompt(x)) as a query vector to find k-Nearest Neighbors N;   computing a probability distribution {circumflex over (p)} kNN  of results from the k-Nearest Neighbor search, wherein {circumflex over (p)} kNN  is computed as:   
       
         
           
             
               
                 
                   p 
                   ^ 
                 
                 kNN 
               
               = 
               
                 
                   1 
                   
                     
                       ❘ 
                       "\[LeftBracketingBar]" 
                     
                     N 
                     
                       ❘ 
                       "\[RightBracketingBar]" 
                     
                   
                 
                 ⁢ 
                 
                   
                     ∑ 
                     
                       ( 
                       
                         _ 
                         , 
                         
                           y 
                           ′ 
                         
                         , 
                         
                           
                             h 
                             
                               train 
                               ) 
                             
                           
                           ∈ 
                           N 
                         
                       
                     
                   
                   
                     
                       
                         y 
                         = 
                         
                           y 
                           ′ 
                         
                       
                     
                     
                       exp 
                       ⁡ 
                       ( 
                       
                         
                           - 
                           
                              
                             
                               
                                 h 
                                 train 
                               
                               - 
                               
                                 
                                   h 
                                   LM 
                                 
                                 ( 
                                 
                                   prompt 
                                   ( 
                                   x 
                                   ) 
                                 
                                 ) 
                               
                             
                              
                           
                         
                         T 
                       
                       ) 
                     
                   
                 
               
             
           
         
       
       using T as a scaling hyperparameter;
 interpolating the debiased output probability distribution {circumflex over (p)} debiasedLM  and the probability distribution {circumflex over (p)} kNN  to obtain a final prediction {circumflex over (p)}(y|prompt(x)) for the downstream task; and 
 outputting the results from the k-Nearest Neighbor search to explain the final prediction of the language model. 
 
     
     
         10 . The computer program product of  claim 9 , wherein parameters of the language model are frozen. 
     
     
         11 . A system for performing a downstream task with a language model comprising a processor, connected to a memory, operable to perform:
 obtaining a dataset for the downstream task, the dataset comprising at least a training set and a testing set;   constructing a datastore by applying the language model to the training set, the datastore comprising a set of triplets with each triplet including an instance x train  from the training set, a label y′, and a feature vector h train , and wherein the feature vector h train  corresponds to a masked token in the sentence x train ;   applying the language model to a prompt-applied sentence prompt(x) from an instance x in the testing set to predict a label y and a large language model feature vector h LLM (prompt(x));   computing an output probability distribution P LM  of the language model;   debiasing the output probability distribution P LM  of the language model to obtain a debiased output probability distribution {circumflex over (p)} debiasedLM ;   performing a k-Nearest Neighbor search of the datastore using the feature vector h LLM (prompt(x)) as a query vector to find k-Nearest Neighbors N;   computing a probability distribution {circumflex over (p)} kNN  of results from the k-Nearest Neighbor search, wherein {circumflex over (p)} kNN  is computed as:   
       
         
           
             
               
                 
                   p 
                   ^ 
                 
                 kNN 
               
               = 
               
                 
                   1 
                   
                     
                       ❘ 
                       "\[LeftBracketingBar]" 
                     
                     N 
                     
                       ❘ 
                       "\[RightBracketingBar]" 
                     
                   
                 
                 ⁢ 
                 
                   
                     ∑ 
                     
                       ( 
                       
                         _ 
                         , 
                         
                           y 
                           ′ 
                         
                         , 
                         
                           
                             h 
                             
                               train 
                               ) 
                             
                           
                           ∈ 
                           N 
                         
                       
                     
                   
                   
                     
                       
                         y 
                         = 
                         
                           y 
                           ′ 
                         
                       
                     
                     
                       exp 
                       ⁡ 
                       ( 
                       
                         
                           - 
                           
                              
                             
                               
                                 h 
                                 train 
                               
                               - 
                               
                                 
                                   h 
                                   LM 
                                 
                                 ( 
                                 
                                   prompt 
                                   ( 
                                   x 
                                   ) 
                                 
                                 ) 
                               
                             
                              
                           
                         
                         T 
                       
                       ) 
                     
                   
                 
               
             
           
         
       
       using T as a scaling hyperparameter;
 interpolating the debiased output probability distribution {circumflex over (p)} debiasedLM  and the probability distribution {circumflex over (p)} kNN  to obtain a final prediction {circumflex over (p)}(y|prompt(x)) for the downstream task; and 
 outputting the results from the k-Nearest Neighbor search to explain the final prediction of the language model. 
 
     
     
         12 . The computer program product of  claim 9 , further comprising:
 extracting an instance x from the testing set; and   applying a prompt to the instance x to obtain the prompt-applied sentence prompt(x).   
     
     
         13 . The computer program product of  claim 9 , wherein the label y is predicted from a pre-defined label set Y. 
     
     
         14 . The computer program product of  claim 13 , wherein the output probability distribution P LM  is computed over a vocabulary V as P LM (y=V prompt(x)). 
     
     
         15 . The computer program product of  claim 9 , wherein {circumflex over (p)} debiasedLM =W debias P LM (y∈V|prompt(x)), wherein W debias =diag({circumflex over (p)} cf ) −1  in which diag(v) is a function that returns a diagonal matrix of v, and wherein {circumflex over (p)} cf  is computed from {circumflex over (p)} cf =1/C Σc=1   C P LM (y|prompt(context c )) by giving different input texts prompt(context c )) to the language model where context c  is context-free input. 
     
     
         16 . The computer program product of  claim 9 , wherein k is a number of instances, and wherein k∈{0, 1, 4, 8}. 
     
     
         17 . The computer program product of  claim 9 , wherein {circumflex over (p)}(y|prompt(x))=λ*{circumflex over (p)} debiasedLM +(1−λ)*{circumflex over (p)} kNN , and wherein λ∈[0,1]. 
     
     
         18 . The system of  claim 11 , wherein parameters of the language model are frozen. 
     
     
         19 . The system of  claim 11 , further comprising:
 extracting an instance x from the testing set; and   applying a prompt to the instance x to obtain the prompt-applied sentence prompt(x).   
     
     
         20 . The system of  claim 11 , wherein the label y is predicted from a pre-defined label set Y. 
     
     
         21 . The system of  claim 20 , wherein the output probability distribution P LM  is computed over a vocabulary V as P LM (y∈V|prompt(x)). 
     
     
         22 . The system of  claim 11 , wherein {circumflex over (p)} debiasedLM =W debias  P LM (y∈V|prompt(x)), wherein W debias =diag ({circumflex over (p)} cf ) −1  in which diag(v) is a function that returns a diagonal matrix of v, and wherein {circumflex over (p)} cf  is computed from {circumflex over (p)} cf =1/C Σc=1   C P LM (y|prompt(context c )) by giving different input texts prompt(context c ) to the language model where context c  is context-free input. 
     
     
         23 . The system of  claim 11 , wherein k is a number of instances, and wherein k∈{0,1,4,8}. 
     
     
         24 . The system of  claim 11 , wherein {circumflex over (p)}(y|prompt(x))=λ*{circumflex over (p)} debiasedLM +(1−λ)*{circumflex over (p)} kNN , and wherein λ∈[0,1].

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